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World's largest snake shows tropics were hotter in the past

05.02.2009

The largest snake the world has ever known -- as long as a school bus and as heavy as a small car -- ruled tropical ecosystems only 6 million years after the demise of the fearsome Tyrannosaurus rex, according to a new discovery published in the journal Nature.

Partial skeletons of a new giant, boa constrictor-like snake named "Titanoboa" found in Colombia by an international team of scientists and now at the University of Florida are estimated to be 42 to 45 feet long, the length of the T-Rex "Sue" displayed at Chicago's Field Museum, said Jonathan Bloch, a UF vertebrate paleontologist who co-led the expedition with Carlos Jaramillo, a paleobotanist from the Smithsonian Tropical Research Institute in Panama.

Researchers say the extinct snake was even larger than the wildest dreams of directors of modern horror movies.

"Truly enormous snakes really spark people's imagination, but reality has exceeded the fantasies of Hollywood," said Bloch, who is studying the snake at the Florida Museum of Natural History on the UF campus. "The snake that tried to eat Jennifer Lopez in the movie 'Anaconda' is not as big as the one we found."

Jason Head, a paleontologist at the University of Toronto in Mississauga and the paper's senior author, described it this way: "The snake's body was so wide that if it were moving down the hall and decided to come into my office to eat me, it would literally have to squeeze through the door."

Besides tipping the scales at an estimated 1.25 tons, the snake lived during the Paleocene Epoch, a 10-million-year period immediately following the extinction of the dinosaurs 65 million years ago, Bloch said.

The scientists also found many skeletons of giant turtles and extinct primitive crocodile relatives that likely were eaten by the snake, he said. "Prior to our work, there had been no fossil vertebrates found between 65 million and 55 million years ago in tropical South America, leaving us with a very poor understanding of what life was like in the northern Neotropics," he said. "Now we have a window into the time just after the dinosaurs went extinct and can actually see what the animals replacing them were like."

Size does matter because the snake's gigantic dimensions are a sign that temperatures along the equator were once much hotter. That is because snakes and other cold-blooded animals are limited in body size by the ambient temperature of where they live, Bloch said.

"If you look at cold-blooded animals and their distribution on the planet today, the large ones are in the tropics, where it's hottest, and they become smaller the farther away they are from the equator," he said.

Based on the snake's size, the team was able to calculate that the mean annual temperature at equatorial South America 60 million years ago would have been about 91 degrees Fahrenheit, about 10 degrees warmer than today, Bloch said.

The presence of outsized snakes and turtles shows that even 60 million years ago the foundations of the modern Amazonian tropical ecosystem were in place, he said.

Fossil hunting is usually difficult in the forest-covered tropics because of the lack of exposed rock, Bloch said. But excavations in the Cerrejon Coal Mine in Northern Colombia exposed the rock and offered an unparalleled opportunity for discovery, he said.

After the team brought the fossils to the Florida Museum of Natural History, it was UF graduate students Alex Hastings and Jason Bourque who first recognized they belonged to a giant snake, Bloch said. Head, an expert on fossil snakes, worked with David Polly, a paleontologist at the University of Indiana, to estimate the snake's length and mass by determining the relationship between body size and vertebral -- backbone -- size in living snakes and using that relationship to figure out body size of the fossil snake based on its vertebrae.

Harry W. Greene, professor in the department of ecology and evolutionary biology at Cornell University and one of the world's leading snake experts, said the "colossal" ancient boa researchers found has "important implications for snake biology and our understanding of life in the ancient tropics."

"The giant Colombian snake is a truly exciting discovery," said Greene, who wrote the book "Snakes: The Evolution of Mystery in Nature." "For decades herpetologists have argued about just how big snakes can get, with debatable estimates of the max somewhat less than 40 feet."

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